drm: Make drm_fb_unregister/remove accept NULL fb

These functions are used by drivers to release fbdev emulation
buffers. We need to make them resilient to NULL pointers to
make the fbdev compile/runtime knobs not cause Oopses on module
unload.

Cc: Archit Taneja <architt@codeaurora.org>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 33d877c65ced6a3c138af9ab47c824038410be0b..884690c8109427aa7764bc50143363ede71c00a7 100644 (file)
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -538,7 +538,12 @@ EXPORT_SYMBOL(drm_framebuffer_reference);
  */
 void drm_framebuffer_unregister_private(struct drm_framebuffer *fb)
 {
-       struct drm_device *dev = fb->dev;
+       struct drm_device *dev;
+
+       if (!fb)
+               return;
+
+       dev = fb->dev;
 
        mutex_lock(&dev->mode_config.fb_lock);
        /* Mark fb as reaped and drop idr ref. */
@@ -589,12 +594,17 @@ EXPORT_SYMBOL(drm_framebuffer_cleanup);
  */
 void drm_framebuffer_remove(struct drm_framebuffer *fb)
 {
-       struct drm_device *dev = fb->dev;
+       struct drm_device *dev;
        struct drm_crtc *crtc;
        struct drm_plane *plane;
        struct drm_mode_set set;
        int ret;
 
+       if (!fb)
+               return;
+
+       dev = fb->dev;
+
        WARN_ON(!list_empty(&fb->filp_head));
 
        /*